Reserves for Future Policy Benefits (Details) - Annuitization Benefit - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning Balance	$ 713	$ 322
Incurred	10	20
Paid	8	10
Change in Unrealized Investment Gains and Losses	(37)	(10)
Ending Balance	678	322
Movement in Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable [Roll Forward]
Beginning Balance	26	28
Incurred	8	2
Paid	0	0
Ending Balance	$ 34	$ 30